Generally a transmit/receive module used in a radar apparatus has circuits for monitoring a transmit line and monitoring a receive line as well as circuits for amplifying a transmit signal and amplifying a receive signal.
FIG. 12 shows a conventional transmit/receive module. In transmit/receive module 200, transmit input terminal 202 is connected to exciter 206 via power distributor 204, receive output terminal 208 is connected to receiver 212 via power combiner 210 and monitoring input/output terminal 214 is connected to measurement apparatus 218 via power distributor/combiner 216. Transmit output/receive input terminal 226 is connected to an antenna (not shown).
A plurality of transmit/receive modules (not shown) are provided. Each of the transmit input terminals is connected to power distributor 204, each of receive terminals is connected to power combiner 210 and each of monitoring input/output terminals is connected to power distributor/combiner 216.
During transmitting, a transmit signal inputted to transmit input terminal 202 via power distributor 204 from exciter 206 is amplified by transmit amplifier 220, and is outputted to transmit output/receive input terminal 226 via transmit/receive separator 222 and branch device 224.
During receiving, a signal inputted to transmit output/receive input terminal 226 is amplified by receive amplifier 228 via branch device 224 and transmit/receive separator 222, and is outputted to receive output terminal 208 and is inputted to receiver 212 via power combiner 210.
During monitoring a transmit line and a receive line, a measurement apparatus, for example, is used instead of exciter 206 and receiver 212. During monitoring the transmit line, a standard signal is inputted to transmit input terminal 202 via power distributor 204 from the measurement apparatus (not shown). A part of amplified standard signal is outputted to monitoring input/output terminal 214 through the transmit amplifier 220, transmit/receive separator 222, and branch device 224. And amplified standard signal is inputted to measurement apparatus 218 via power distributor/combiner 216 connected to monitoring input/output terminal 214, and a gain of transmit amplifier 220 and passband phase characteristic, etc. are monitored by measurement apparatus 218.
During monitoring a receive line, the standard signal is inputted to monitoring input/output terminal 214 via power distributor/combiner 216 from measurement apparatus 218. An amplified standard signal is outputted to receive terminal 208 through branch device 224, transmit/receive separator 222, and receive amplifier 228. And amplified standard signal is inputted to a measurement apparatus (not shown) via power combiner 210 connected to receive output terminal 208, and a gain of receive amplifier 228 and passband phase characteristic, etc. are monitored by the measurement apparatus.
According to existing transmit/receive module 200, monitoring input/output terminal 214 only for measuring apparatus is required, and power distributor/combiner 216 only for measuring apparatus is still required outside. For this reason, the radar apparatus becomes large and there is a problem that reduction in size and weight of the radar apparatus is difficult.